I want to be able to create a smooth transition to ladders/overhead poles and such - what is the best and most accurate way of doing this?

I have the majority of other systems in place for my platformer, including actions I thought would be more difficult, yet this one aspect has baffled me! When a player reaches a ladder or an overhead bar for example, I wish to move them into position onto that object and then allow them to move along it or up and down it. Obviously the simplest form of this would be to set the X or Y value of the player upon overlap and then 'drop' the player when an overlap is no longer occuring - so what is the best way to make this transition nice and smooth and how should I handle exiting this state also? Any help would be greatly appreciated as it would mean all my gameplay mechanics are ready and I can finally build my levels!